College represents a unique vulnerability period for the development of body dissatisfaction (BD) and disordered eating among women. Research has suggested that these public health concerns may be at least partly explained by social comparison and objectification theories, two prominent social psychological theories. Humans engage in social comparisons with others in order to understand how and where they fit into the world. Objectification theory holds that the feminine body has been constructed as an object to be gazed upon; given this, females learn to view themselves from an observer's perspective and to treat themselves as objects to be looked at. This proposal will extend previous research by examining how these two theories fit into an elaborated version of Stice's (1994) socio-cultural model of disordered eating and by using an experience sampling/ecological momentary assessment (EMA) approach, which involves assessing participants multiple times per day in their natural environments. Specifically, this proposal will use novel methodology (i.e., EMA), test social comparison and objectification as factors that may explain the relation between thin ideal internalization and BD in the socio-cultural model of disordered eating, and utilize rigorous prospective analyses - doing these 3 things will fill important gaps in the literature. A sample of 200 college women will participate, which will include 2 self-report questionnaire sessions (at the start and end of an academic semester) and a 2-week EMA component (i.e., via their personal computers, participants will complete a short set of questions 3x/daily mid-semester). Constructs assessed will include: pressure for thinness, thin ideal internalization, social comparison, body surveillance (the indicator of objectification), BD, and disordered eating. Key hypotheses: 1) increases in momentary social comparison and body surveillance will be associated with subsequent increases in BD and disordered eating; 2) momentary instances of social comparison and body surveillance will mediate the relation between thin ideal internalization and BD; 3) a socio-cultural model incorporating social comparison and body surveillance will provide a better fit to the data than a model that does not incorporate these constructs. Multilevel and structural equation modeling will be utilized to test these hypotheses. Results may inform future prevention programs for college women by identifying relevant and mutable behaviors that impact BD/disordered eating.